GM to merge Zeta and Sigma chassis

One of the oddities of GM’s platform strategy is that they have two large rear-drive architectures that are similar in size. Sigma and Zeta.

Sigma is Cadillac’s dedicated rear-drive chassis that debuted in 2003 on the original CTS and has seen duty under the SRX, STS, and the new 2nd generation CTS. It’s two downsides are that it is relatively expensive and can’t be shared with other, higher volume models (some would call this a benefit) and that the chassis can’t be expanded much beyond the size of the current STS.

Zeta is GM’s latest rear-drive architecture that was developed primarily by GM’s Holden division and is aimed at the lower costs needed by volume brands such as Holden, Pontiac, Chevrolet, etc.

According to MotorTrend.com, GM has decided to merge the development of these two chassis.

By planning the merged architecture for both luxury and volume models, they will be able to cut costs of all models without giving up the premium features that Cadillac customers expect.

Additionally, GM is still expected to be working on the Alpha chassis in standard and premium versions for the Cadillac 3-Series competitor and also smaller rear-drive models for Holden, Pontiac, and Chevy.